The Spear & Jackson Filter Replacement is specifically designed for the 42265 Spear & Jackson air purifier. This HEPA filter effectively eliminates airborne allergens such as dust and pollen, while also eliminating unpleasant odours. It is recommended to replace the filter every 1000 hours or every six months. Once the filter has been used for 1000 hours, the filter change indicator light will turn red to remind you to replace it. After replacing the air purifier filter, simply press the 'filter reset' button on the device for three seconds. When it's time to replace the filter, rotate the bottom cover counter clockwise to open it, remove the old filter, insert the new filter, and then rotate the bottom cover clockwise to lock it back into place. To maintain the highest standards of air purification for your air purifier, we suggest removing and cleaning the existing filter with a vacuum cleaner approximately once a month. This filter measures 15 x 15 x 12.3cm.